PROJECT SUMMARY/ABSTRACT This K23 application proposes focused training and research to facilitate the applicant?s transition to an independent scientist focused on developing innovative, engaging, and impactful digital health interventions (DHIs) for high-risk smokers?including those with social anxiety. CONTEXT: Individuals with social anxiety? those who meet full diagnostic criteria for social anxiety disorder (SAD) as well as those with subthreshold symptoms of SAD)?are an understudied and undertreated group of smokers. An estimated 14.6 million (36%) adult smokers in the United States meet lifetime criteria for SAD. Compared to the general population, socially anxious smokers have double the prevalence rates of smoking (33% vs. 17%) and are less likely to remain abstinent (29% vs. 36%). However, there are no targeted interventions for this high-risk group. Although digital health interventions (DHIs) offer an ideal treatment modality for these smokers, engagement with DHIs is strikingly low. Because greater engagement with DHIs is associated with better cessation outcomes, the full potential of DHIs for smoking is far from realized and research is needed to optimize engagement with these interventions in ways that improve outcomes. A single approach to increasing engagement is unlikely to be efficacious for all smokers. Adaptive treatment strategies (ATSs) that allow flexibility in what intervention components are offered over time to different smokers based on their individualized needs hold promise for improving effective engagement with and effectiveness of these interventions. RESEARCH STRATEGY: Building upon the applicant?s NIDA F32 project in which she is developing the core content of a targeted web intervention for socially anxious smokers (MyWebQuit), the objective of the current proposal is to develop and assess the feasibility and acceptability of new engagement components that will be ultimately be sequenced to comprise an ATS for improving engagement with and effectiveness of MyWebQuit. The project includes phases to: (1) develop the new components to enhance engagement using an iterative, user-centered design approach (Aim1), and (2) conduct a pilot sequential multiple assignment randomized trial (SMART) to assess: the feasibility of conducting a full-scale SMART, the acceptability and utilization of the new components, the potential impact on process (website utilization) and cessation outcomes, and explore secondary tailoring variables that may enable a more deeply tailored ATS (Aim2). TRAINING PLAN: To achieve her short- and long-term career goals, this proposal will provide the applicant with advanced training in the following: (1) theory and science of improving engagement with DHIs, (2) experimental methods that inform the construction of high-quality ATSs, and (3) conduct, management, and analysis of clinical trials involving DHIs for vulnerable groups of smokers. These goals will be accomplished through close mentorship from experts in these areas, carefully selected didactic activities and conference attendance, applied research experiences, and manuscript and grant proposal (i.e. an R01 for a fully-powered SMART) preparation.